Charlie bit me again!

An example of everyday neurobiology in action

Submitted by Marica Marais

Date: 19 July 2014

Image from: www.ecodentistryblog.com

The video

https://www.youtube.com/watch?v=_OBlgSz8sSM

The video is called “Charlie bit me again” and is

available on Youtube or by clicking on the hyperlink.

The video

The main events that will be my focus in this video (in summary):

1. The baby brother bites lightly on the little boy’s left index finger and the boy reacts to this light touch by changing his facial expression (laughing) and by saying “Charlie! Charlie bit me!” with a smile on his face

2. The boy now places his right index finger in his baby brother’s mouth- voluntary movement

3. This time, the baby brother bites lightly at first and then bites down (apparently quite hard)

4. The boy responds to this change in touch (from pleasant to painful) by changing his facial and verbal expression from smiling/softly giggling to frowning and shouting loudly: “ouch…ouch…Ouch, Charlie, OUCH OOOOOOOUUUUUUCH!”

5. I will focus on how the three long pathways that we’ve learned about are activated in the older boy

The three long pathways as

shown in this example

Pathway 1: Voluntary movement

Pathway 2: Light touch

Pathway 3: Painful touch

1. Voluntary movement: Boy

moves finger

In the video clip there is one specific movement I want to focus on:

When the boy places his right finger in his baby brother’s mouth (the second time)

This is a voluntary movement which starts in the left telencephalon(motor cortex). The information travels from this area of the cortex via the neuron and crosses in the brainstem to the right side of the body where it moves down the cervical spinal cord and synapses with a motor neuron. This motor neuron then activates the muscle to move the finger into the brother’s mouth.

This cortico-spinal pathway consists of 2 neurons. This pathway is specifically important for intentional, fine movements of the distal limbs (e.g. The fingers)

Boy moves finger:

How the message travels

Place of origin

Cerebrospinal cortex/telencephalon/motor cortex

Number of neurons involved

Two per pathway

Place of synapse

Brainstem

End destination of message

Muscle

Effect

Movement of finger

2. Light touch

In this video there are two main sensations that are experienced by the boy, namely

light touch and pain (with varying degrees of intensity, of course).

These sensations travel via two separate pathways.

In this video the boy experiences the light bite in the following way:

When his brother bites his left (and his right finger initially) lightly, the information

enters the spinal cord via the spinal nerve in the finger. The message travels up

through the spinal cord on the same side (left for the left finger and right for the right

finger) and synapses with a neuron in the brain stem, where it crosses the midline.

Now it travels via the second neuron to the thalamus, where the message is

‘translated’ so that the somatosensory cortex will be able to receive it. Lastly it travels

to the somatosensory cortex (on the opposite side of the bitten finger) where it

registers as light touch.

The somatosensory pathway consists of 3 neurons.

Light touch experience:

How the message travels

Place of origin

The sensory neurons in the boys finger

Number of neurons involved

Three per pathway

Places of synapse

Brainstem, thalamus

End destination of message

Somatosensory cortex

Effect

Light touch is experienced – boy reacts by showing enjoyment

3. Pain

In this video there are two main sensations that are experienced by the boy, namely light touch and pain (with varying degrees of intensity, of course).

These sensations travel via two separate pathways.

In this video the boy experiences the painful bite in the following way:

When his brother bites down hard the boy’s right finger, the information enters the spinal cord via the spinal nerve in the finger. The message immediately contacts a neuron in the spinal nerve, crossing the midline. It then travels up through the spinal cord on the opposite side (left for the right bitten finger) and synapses with a neuron in the brain stem. Now it travels via a second neuron to the thalamus, where the message is ‘translated’ so that the somatosensory cortex will be able to receive it. Lastly it travels via a third neuron to the left somatosensory cortex (on the opposite side of the bitten finger), where it registers as pain.

The somatosensory pathway consists of 3 neurons.

Pain experience:

How the message travels

Place of origin

The somatosensory neurons in the boy’s finger

Number of neurons involved

Three per pathway

Places of synapse

Spinal cord, thalamus

End destination of message

Somatosensory cortex

Effect

Pain is experienced – boy reacts by showing distress

How this course has helped me to

analyze events and phenomena

I have learned more about the development of the nervous system in utero, which has helped me to start thinking about how the anatomy of the nervous system plays a significant role in how it functions. I found that section fascinating and will definitely be reading more about it.

I have learned to look at the location of symptoms as an indication of where the injury might be in the nervous system. This has helped me to pay more attention to whether symptoms are on the right or left side of the body, for example.

I have come to know more about the functioning the three pathways, which I have been noticing in events around me more and more.

I have also started to become more aware of facial expressions and their significance. Although this course did not go into a lot of detail about this, I found this very intriguing and have started paying more attention to whether facial expressions are reflexive, forced, etc.